[TowerTalk] Which better: TOP of hill or SIDE of hill?

[Guy Olinger, K2AV]

This will not be a question with a simple answer.

You need to obtain a terrain analysis program, such as HFTA, which 
comes with the ARRL Antenna Book.

Both optimum placement of the antenna relative to the slope, and 
optimum tower height can be COUNTER-INTUITIVE, and are remarkably 
variable depending on the specifics of the foreground terrain.

With the program in hand, you can try various placements and heights 
and see the results. I believe that HFTA can use USGS terrain files 
and give you very specific data for your situation.

HFTA will take your entire situation into consideration.

I would not under any circumstances commit yourself to any 
configuration until you have done a very careful HFTA analysis of your 
situation.

73, Guy.



----- Original Message ----- 
From: "John WA2GO" <xnewyorka at hotmail.com>
To: <towertalk at contesting.com>
Sent: Monday, December 27, 2004 10:02 AM
Subject: [TowerTalk] Which better: TOP of hill or SIDE of hill?


> My new qth-to-be has a north-south ridgeline running through the 
> center of the property.
> I can put towers right on the ridgeline at 600' ASL, or I can put 
> towers down the sides of each hill. In the latter case, I would have 
> an Europe/Africa/S. America at 550' with 50' of hill rising behind 
> it, and a US/Asia/Oceania/S. America tower at 530' on the West side, 
> with 70' of hill rising behind it.
> (This setup also puts the East and West towers 700' apart!)
>
> Question is: Which is best?
>  a) being on the hilltop,
>  b) being on the precipice of the drop-off, or
>  c) being partway down a 250' slope, with 50' - 70' of hill sloping 
> up behind the tower.
>
> (Yes, it slopes down 250' to both East and West, as well as North!!)
>
> I would experiment with dipoles, but I can't really experiment now, 
> because I don't own the property yet.  Also, I imagine the answer 
> might be different for 40M vs. 10M.  I can have a single tower for 
> each band if necessary/best.
>
> I am in the permitting process, and I want to apply for what I 
> really need in order to maximize my chances for approval.
>
> Is there modeling software I can use that takes into account the 
> terrain BEHIND the beam?  If so, which one?  Anybody out there 
> already done this modeling, or better yet, already done real-world 
> experimentation?   Intuition says having slope up behind beam is 
> good, but that's only intuition. Wondering if it is, how much slope 
> is needed in order to be worthwhile, on each band.
>
> Thanks!
>
> John
> WA2GO
>
>
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